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Old 20th June 2004, 08:05 PM   #1
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Default GC SuperSymmetry

For those who didn't find "Monolithic SuperSymmetry" interesting
enough, I present a concept schematic which uses power chips
such as the LM3875 or 3886 (or anything else, for that matter).
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Old 20th June 2004, 08:44 PM   #2
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Have you tested it in real life? Pros and cons?
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Old 20th June 2004, 08:53 PM   #3
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Whatabout replace this " bloody " transistors by two OPA 660 ?
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Old 20th June 2004, 09:29 PM   #4
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Hmm
Nice to see another variant of simplicity to play with.
As stated, supersymmetry works best with simple circuits.
Is the complexity of such an LM38xx not an issue?

/Hugo
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Old 20th June 2004, 09:59 PM   #5
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Default Re: GC SuperSymmetry

Quote:
Originally posted by Nelson Pass
For those who didn't find "Monolithic SuperSymmetry" interesting
enough, I present a concept schematic which uses power chips
such as the LM3875 or 3886 (or anything else, for that matter).

Is this an offshoot of looking into lowcost solutions to audio equipment? I have been wondering what topology is used in the FirstWatt amplifier.

George
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Old 21st June 2004, 12:49 AM   #6
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Quote:
Originally posted by Netlist
Nice to see another variant of simplicity to play with.
As stated, supersymmetry works best with simple circuits.
Is the complexity of such an LM38xx not an issue?
/Hugo
Setting the gain around each Chip Amp via the - input loop
allows quite a bit of adjustment in this regard. The Chip
Amps are of course enclosed in the loop formed by the diff
pair, and so their distortions will tend to be nulled, reducing the
overall effect toward the performance of the diff pair itself.

I hope you guys appreciate that I used Bipolar transistors
just for the occasion.
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Old 21st June 2004, 12:51 AM   #7
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Default Re: Re: GC SuperSymmetry

Quote:
Originally posted by Panelhead
Is this an offshoot of looking into lowcost solutions to audio equipment? I have been wondering what topology is used in the FirstWatt amplifier.
1) No.

2) No chip amps currently on the FW drawing board. FW
offerings will initially be single-stage discrete.
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Old 21st June 2004, 03:53 AM   #8
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Mr Pass,

You never run out of ideas, don't you.
There are 2 feedback loops, one is around each differential transistor (set by 2 resistors) and the other one is around (-) input of the GC (also set by 2 resistors).
What is the good proportion of gain between these 2 feedback system?. Usually the one around GC is bigger. But by how much (compared to the one in the differential) is the best?

Also in this kind of system, every GC will see only half the impedance of the speaker. If the speaker is 8ohm, each will see 4ohm. But if the speaker is 4ohm, each will see 2ohm. GC chips cannot stand this low impedance. Is there any current boosting method so that this power amp can work with 4ohm speakers?
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Old 21st June 2004, 04:20 AM   #9
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Interesting design. While some of the SuSy design have problem with absolute DC offset, in this design, there is no R at all at differential to ground.
The only ground reference can be found in GC input/output. Is this the one who sets the 0 point of the whole system?
Also no "magic resistors" needed from each outputs to CCS of differential?
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Old 21st June 2004, 07:20 AM   #10
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Beutiful- I have been waiting for this.
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